Strongly-Typed Configuration For .NET Core – With Full Dependency Injection Support

Configuration is one of the most prominent cornerstones in software systems, and especially in distributed systems. And it has been a point for discussions in .NET for quite some time.

In diesem Artikel:

Strongly-Typed Configuration For .NET Core – With Full Dependency Injection Support
Pawel Gerr ist Architekt und Consultant bei Thinktecture. Er hat sich auf .NET Core Backends spezialisiert und kennt Entity Framework von vorne bis hinten.

In one of our projects we have built a solution that lets different applications in different companies exchange data, although being behind firewalls, using the open source Relay Server. But, to our surprise, one of the features our customer was amazed about was the library I’ve developed to make configuration easier to handle.

In Thinktecture.Configuration I’ve taken over the ideas, generalized them and added new features.

The basic idea is that .NET developers should be able to deal with configuration data by just using arbitrary classes.

The library consists of 3 main components: IConfigurationLoaderIConfigurationProvider and IConfigurationSelector. The IConfigurationLoader loads data from storage, e.g. JSON from the file system. The IConfigurationProvider uses IConfigurationSelector to select the correct piece of data like a JSON property and to convert this data to requested configuration.

In short, the features of the lib are:

  • The configuration (i.e. the type being used by the application)

    • should be type-safe
    • can be an abstract type (e.g. an interface)
    • don’t have to have property setters or other kind of metadata just to be deserializable
    • can be and have properties that are virtually as complex as needed
    • can be injected via DI (dependency injection)
    • can have dependencies that are injected via DI (i.e. via constructor injection)
    • can be changed by „overrides“
  • The usage of the configuration in a developer’s code base should be free of any stuff from the configuration library
  • The extension of a configuration by new properties or changing the structure of it should be a one-liner

Use Cases

In this post I’m going to show the capabilities of the library by illustrating it with a few examples. In this concrete example I’am using a JSON file containing the configuration values (with Newtosonf.Json in the background) and Autofac for DI.

But the library is not limited to these. The hints are at the end of this post if you want to use a different DI framework, other storage than the file system (i.e. JSON files) or not use JSON altogether.

The first use case is a bit lengthy to explain the basics. The others will just point out specific features.

Want to see the code? Go to Thinktecture.Configuration

Nuget: Install-Package Thinktecture.Configuration.JsonFile.Autofac

1. One file containing one or more configurations

Shown features in this example:

  • one JSON file
  • multiple configurations
  • a configuration doesn’t have to be on the root of the JSON file
  • a configuration has dependencies known by DI
  • a configuration gets injected in a component like any other dependency

We start with 2 simple configuration types.

				
					public interface IMyConfiguration
{
    string Value { get; }
}

public interface IOtherConfiguration
{
    TimeSpan Value { get; }  
}
				
			

The configuration IMyConfiguration is required by our component MyComponent.

				
					public class MyComponent
{
    public MyComponent(IMyConfiguration config)
    {
    }
}
				
			

Configuration file configuration.json

				
					{
    "My":
    {
        "Config": { value: "content" }
    },
    "OtherConfig": { value: "00:00:05" }
}
				
			

Now let’s setup the code in the executing assembly and configure DI to make MyComponent resolvable along with IMyConfiguration .

				
					var builder = new ContainerBuilder();
builder.RegisterType<MyComponent>().AsSelf();

// IFile is required by JsonFileConfigurationLoader to access the file system
// For more info: https://www.nuget.org/packages/Thinktecture.IO.FileSystem.Abstractions/
builder.RegisterType<FileAdapter>().As<IFile>().SingleInstance();

// register so-called configuration provider that operates on "configuration.json"
builder.RegisterJsonFileConfigurationProvider("./configuration.json");

// register the configuration.
// "My.Config" is the (optional) path into the config JSON structure because our example configuration does not start at the root of the JSON
builder.RegisterJsonFileConfiguration<MyConfiguration>("My.Config")
    .AsImplementedInterfaces() // i.e. as IMyConfiguration
    .SingleInstance(); // The values won't change in my example

// same difference with IOtherConfiguration
builder.RegisterJsonFileConfiguration<OtherConfiguration>("OtherConfig")
    .AsImplementedInterfaces();

var container = builder.Build();
				
			

 The concrete types MyConfiguration and OtherConfiguration are, as often when working with abstractions, used with DI only. Apart from that, these types won’t show up at any other places. The type MyConfiguration has a dependency IFile that gets injected during deserialization.

				
					public class MyConfiguration : IMyConfiguration
{
    public string Value { get; set; }

    public MyConfiguration(IFile file)
    {
        ...
    }
}

public class OtherConfiguration : IOtherConfiguration
{
    public TimeSpan Value { get; set; }  
}
				
			

 The usage is nothing special

				
					// IMyConfiguration gets injected into MyComponent
var component = container.Resolve<MyComponent>();

// we can resolve IMyConfiguration directly if we want to
var config = container.Resolve<IMyConfiguration>();
				
			

2. Nesting

Shown features in this use case:

  • one of the properties of a configuration type is a complex type
  • complex property type can be instantiated by Newtonsoft.Json or DI
  • complex property can be resolved directly if required

In this example IMyConfiguration has a property that is not of a simple type. The concrete types implementing IMyConfiguration and IMyClass consist of property getters and setters only thus left out for brevity.

				
					public interface IMyConfiguration
{
    string Value { get; }
    IMyClass MyClassValue { get; }
}

public interface IMyClass
{
    int Value { get; }  
}
				
			

The JSON file looks as following:

				
					{
    "Value": "content",
    "MyClassValue": { "Value": 42 }
}
				
			

Having a complex property we can decide whether the type IMyClass is going to be instantiated by Newtonsoft.Json or DI.

With just the following line the type IMyClass is not introduced to the configuration library and is going to be instantiated by Newtonsoft.Json.

				
					builder.RegisterJsonFileConfiguration<MyConfiguration>()
    .AsImplementedInterfaces()
    .SingleInstance();

				
			

With the following line we introduce the type to the config lib and DI but the instance of IMyClass cannot be resolved directly.

				
					builder.RegisterJsonFileConfigurationType<MyClass>();
				
			

Should IMyClass be resolvable directly then we can use the instance created along with IMyConfiguration or let new instance be created.

				
					// option 1: use the property of IMyConfiguration
builder.Register(context => context.Resolve<IMyConfiguration>().MyClassValue)
    .AsImplementedInterfaces()
    .SingleInstance();

// option 2: let create a new instance 
builder.RegisterJsonFileConfiguration<MyClass>("MyClassValue")
    .AsImplementedInterfaces()
    .SingleInstance();
				
			

3. Multiple JSON files

The configurations can be loaded from more than one file.

Configuration types are

				
					public interface IMyConfiguration
{
    string Value { get; }
}

public interface IOtherConfiguration
{
    TimeSpan Value { get; }  
}
				
			

File myConfiguration.json

				
					{
    "Value": "content"
}

				
			

File otherConfiguration.json

				
					{
    "Value": "00:00:05"
}
				
			

Having two files we need a means to distinguish between them when registering the configurations. In this case we use Register**Keyed**JsonFileConfigurationProvider that returns a key that will be passed to RegisterJsonFileConfiguration.

				
					var providerKey = builder.RegisterKeyedJsonFileConfigurationProvider("myConfiguration.json");
builder.RegisterJsonFileConfiguration<MyConfiguration>(providerKey)
    .AsImplementedInterfaces()
    .SingleInstance();

var otherKey = builder.RegisterKeyedJsonFileConfigurationProvider("otherConfiguration.json");
builder.RegisterJsonFileConfiguration<OtherConfiguration>(otherKey)
    .AsImplementedInterfaces()
    .SingleInstance();
				
			

4. Overrides

A configuration can be assembled from one base configuration and one or more overrides.

In this case we have two config files. One containing the default values of the configuration and the other containing values to override.

Default values come from baseConfiguration.json

				
					{
    "Value":
    {
        "InnerValue_1": 1,
        "InnerValue_2": 2
    }
}
				
			

InnerValue_2 will be changed by the overrides.json

				
					{
    "Value":
    {
        "InnerValue_2": 3
    }
}
				
			

The configuration 

				
					public interface IMyConfiguration
{
    IInnerConfiguration Value { get; }  
}

public interface IInnerConfiguration
{
    int InnerValue_1 { get; }
    int InnerValue_2 { get; }
}
				
			

To specify overrides we need to provide more than one file path when registering the configuration provider. The overrides are applied in the same order they passed to RegisterJsonFileConfigurationProvider.

				
					builder.RegisterJsonFileConfigurationProvider("baseConfiguration.json", "overrides.json");
builder.RegisterJsonFileConfiguration<MyConfiguration>()
    .AsImplementedInterfaces()
    .SingleInstance();
				
			

5. Extension of the configuration

Let’s add a property to IInnerConfiguration from previous paragraph.

				
					public interface IInnerConfiguration
{
    int InnerValue_1 { get; }
    int InnerValue_2 { get; }
    string NewValue { get; }
}
				
			

Add the corresponding property to the JSON file baseConfiguration.json

				
					{
    "Value":
    {
        "InnerValue_1": 1,
        "InnerValue_2": 2,
        "NewValue": "content"
    }
}
				
			

That’s it.

Working with different frameworks, storages and data models

Using another DI framework

To use a different DI framwork than Autofac use the package Thinktecture.Configuration.JsonFile instead of Thinktecture.Configuration.JsonFile.Autofac and implement the interface IJsonTokenConverter using your favorite DI framework.  The converter has just one method TConfiguration Convert<TConfiguration>(JToken token).

Load JSON from other media

To load JToken from other storages than the file system just implement the interface IConfigurationLoader<JToken,JToken>. For example, if the JSON configuration are in a database then inject the database context or a data access layer and select corresponding data rows.

Use different data models

If you are using other data model than JSON then reference the package Thinktecture.Configuration and implement the interfaces IConfigurationLoader<TRawDataIn,TRawDataOut>IConfigurationProvider<TRawDataIn,TRawDataOut> and IConfigurationSelector<TRawDataIn,TRawDataOut>. It sounds like much but if you look into the code of the corresponding JSON-based classes you will see that the classes are pretty small and trivial.

Some final words...

Although the configuration is an important part of the software development it is not the most exciting one. Therefore, a software developer may be inclined to take shortcuts and work with meaningful hardcoded values. Thinktecture.Configuration gives you the means to work with .NET types without thinking too much how to load and parse the values. This saves time, improves the reusability of the components and the software architecture.

Kostenloser
Newsletter

Aktuelle Artikel, Screencasts, Webinare und Interviews unserer Experten für Sie

Verpassen Sie keine Inhalte zu Angular, .NET Core, Blazor, Azure und Kubernetes und melden Sie sich zu unserem kostenlosen monatlichen Dev-Newsletter an.

Diese Artikel könnten Sie interessieren
.NET
Incremental Roslyn Source Generators in .NET 6: Adapt Code Generation Based on Project Dependencies – Part 5

Incremental Roslyn Source Generators in .NET 6: Adapt Code Generation Based on Project Dependencies – Part 5

The Roslyn Source Generator, implemented in the previous articles of the series, emits some C# code without looking at the dependencies of the current .NET (Core) project. In this article our DemoSourceGenerator should implement a JsonConverter, but only if the corresponding library (e.g. Newtonsoft.Json) is referenced by the project.
08.07.2022
Unterschiede
.NET
Blazor WebAssembly vs. Blazor Server – Welche Unterschiede gibt es und wann wähle ich was?

Blazor WebAssembly vs. Blazor Server – Welche Unterschiede gibt es und wann wähle ich was?

Das Blazor Framework von Microsoft gibt es inzwischen in drei "Geschmacksrichtungen". Die erste ist Blazor WebAssembly, die zweite Blazor Server, und zu guter Letzt gibt es noch Blazor Hybrid. In diesem Artikel wollen wir uns die zwei "echten", also Browser-basierten, Web-Anwendungs-Szenarien WebAssembly und Server anschauen.
04.07.2022
Three different textured walls
.NET
Dependency Injection Scopes in Blazor

Dependency Injection Scopes in Blazor

The dependency injection system is a big part of how modern ASP.NET Core works internally: It provides a flexible solution for developers to structure their projects, decouple their dependencies, and control the lifetimes of the components within an application. In Blazor - a new part of ASP.NET Core - however, the DI system feels a bit odd, and things seem to work a bit differently than expected. This article will explain why this is not only a feeling but indeed the case in the first place and how to handle the differences in order to not run into problems later on.
31.05.2022
.NET
Asynchrone Operationen: Blazor WebAssembly für Angular-Entwickler – Teil 5 [Screencast]

Asynchrone Operationen: Blazor WebAssembly für Angular-Entwickler – Teil 5 [Screencast]

Eine Webanwendung will natürlich auch mit Daten gefüttert werden. Doch diese müssen irgendwo her kommen. Nichts liegt näher als diese von einer Web API zu laden. Dieser Screencast zeigt, wie asynchrone Operationen in Blazor funktionieren und welche gravierenden Unterschiede es zu Angular gibt.
26.05.2022
.NET
Typings: Blazor WebAssembly für Angular-Entwickler – Teil 4 [Screencast]

Typings: Blazor WebAssembly für Angular-Entwickler – Teil 4 [Screencast]

C# und TypeScript entstammen der Feder der selben Person. Doch sind sie deshalb auch gleich? In diesem Teil der Screencast-Serie erfahren Sie, wie mit Typen in den beiden Programmiersprachen verfahren wird und welche Unterschiede es gibt.
19.05.2022
.NET
Bindings: Blazor WebAssembly für Angular-Entwickler – Teil 3 [Screencast]

Bindings: Blazor WebAssembly für Angular-Entwickler – Teil 3 [Screencast]

Wer Komponenten einsetzt, steht früher oder später vor der Fragestellung, wie man Daten an die Komponente übergibt oder auf Ereignisse einer Komponente reagiert. In diesem Screencast wird gezeigt wie Bindings bei Komponenten funktionieren, also wie eine Komponente Daten von außerhalb benutzen und Rückmeldung bei Aktionen geben kann.
12.05.2022